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288

Jul 26, 2010
07/10

by
Armand, Sasan C.; Liao, Mei-Hwa; Morris, Ronald W

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The Space Station Freedom photovoltaic solar array blanket assembly is comprised of several layers of materials having dissimilar elastic, thermal, and mechanical properties. The operating temperature of the solar array, which ranges from -75 to 60 C, along with the material incompatibility of the blanket assembly components combine to cause an elastic-plastic stress in the weld points of the assembly. The weld points are secondary structures in nature, merely serving as electrical junctions...

Topics: CONSISTENCY, DISTRIBUTED PARAMETER SYSTEMS, SIMULATION, SYNCHRONISM, ALGORITHMS, ESTIMATES,...

384
384

Jun 1, 2011
06/11

by
Chavers, D. Gregory; Chang-Diaz, Franklin R.; Irvine, Claude; Squire, Jared P

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Interplanetary travel requires propulsion systems that can provide high specific impulse (Isp), while also having sufficient thrust to rapidly accelerate large payloads. One such propulsion system is the Variable Specific Impulse Magneto-plasma Rocket (VASIMR), which creates, heats, and ejects plasma to provide variable thrust and Isp, designed to optimally meet the mission requirements. The fraction of the total energy invested in creating the plasma, as compared to the plasma's total kinetic...

Topics: MATHEMATICAL MODELS, PROJECT MANAGEMENT, COST ANALYSIS, COST ESTIMATES, AIRBORNE/SPACEBORNE...

285
285

May 23, 2011
05/11

by
Culp, Robert D.; Gravseth, Ian; Gloor, Jason; Wantuch, Tod

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This report documents the status of the Orbital Debris Radar Calibration Spheres (ODERACS) 2 white spheres optical calibration study. The purpose of this study is to determine the spectral reflectivity and scattering characteristics in the visible wavelength region for the white spheres that were added to the project in the fall, 1994. Laboratory measurements were performed upon these objects and an analysis of the resulting data was conducted. These measurements are performed by illuminating...

Topics: DECODING, MAXIMUM LIKELIHOOD ESTIMATES, ALGORITHMS, BINARY CODES, ERROR ANALYSIS, RELIABILITY...

This paper presents new algorithms for estimating the spatio-temporal spectrum of the signals received by a passive array. The algorithms are based on the eigenstructure of the covariance and spectral-density matrices of the received signals. These allow partial correlation between the sources and thus are applicable to certain kinds of multipath problems. Simulation results that illustrate the performance of the new algorithms are presented. (Author)

Topics: DTIC Archive, Wax,M, STANFORD UNIV CA INFORMATION SYSTEMS LAB, *ALGORITHMS, *SPECTRUM ANALYSIS,...

The main findings of the report are: (1) The system set up to handle Government Industry Data Exchange Program (GIDEP) ALERTs within the Air Force is not followed in a consistent fashion. (2) All participants in the GIDEP program are required to report the total yearly savings as part of GIDEP ANNUAL PROGRESS REPORT. The majority cost avoidance are not being reported due to lack of data, lack of personnel or lack of a method to accurately determine savings. (3) the GIDEP participants are...

Topics: DTIC Archive, McCann, T, ANALYTICS INC DAYTON OH, *AVOIDANCE, *COST EFFECTIVENESS, *COST ESTIMATES,...

Two kinds of pole estimators for given noisy transient data are presented. One is a SVD-based methods and the other is the iterative preprocessing algorithm (IPA). The SVD method estimates the characteristic equation coefficients from the weakest eigenvectors when the system order is overdetermined. The IPA is shown to converge to the maximum-likelihood estimator for some range of SNR. It not only reduces the computational burden of the currently existing iterative algorithms but also improves...

Topics: DTIC Archive, Park, Sung-won, NEW MEXICO UNIV ALBUQUERQUE, *SIGNAL PROCESSING, *TRANSIENTS,...

Simulated annealing is a popular Monte Carlo algorithm for combinatorial optimization. The annealing algorithm simulates a nonstationary finite state Markov chain whose state space is the domain of the cost function to be minimized. We analyze this chain focusing on those issues most important for optimization. In all of our results we consider an arbitrary partition optimization: important special cases are when I is the set of minimum cost states or a set of all states with sufficiently small...

Topics: DTIC Archive, Gelfand,Saul B, MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INFORMATION AND DECISION...

This report contains analysis of the direction finding (DF) and fix estimation algorithms in TRAILBLAZER. The TRAILBLAZER software analyzed is old and not currently used in the field. However, the algorithms here analyzed are used in other current IEW systems. The report examines the underlying algorithm assumptions (including unmodeled errors) and their appropriateness for TRAILBLAZER. Coding and documentation problems are then discussed. A detailed error budget is presented. Keywords: Fix...

Topics: DTIC Archive, Gardner, Robert, JET PROPULSION LAB PASADENA CA, *ELECTRONIC WARFARE, *DIRECTION...

The design and the implementation of a real-time communication network has to meet goals of fault-free and timely delivery of messages, as defined by the applications served by this network. The time constraints of the applications are projected as stringent constraints on the local knowledge of time. However, the local knowledge of time in a distributed system requires the use of the communication network. The accuracy and coherence of this knowledge depend on the way clocks are synchronized....

Topics: DTIC Archive, Levi, Shem-Tov, MARYLAND UNIV COLLEGE PARK INST FOR ADVANCED COMPUTER STUDIES,...

An algorithm is presented for the construction of conformal mappings from arbitrary simply-connected regions in the complex plane onto the unit disk. The algorithm is based on a combination of the Kerzman-Stein integral equation and the Fast Multipole Method for the evaluation of Cauchy-type integrals. Previously published methods of this type have an asymptotic CPU time estimate of the order O (n-squared), where n is the number of nodes in the discretization of the boundary of the region being...

Topics: DTIC Archive, O'Donnell, S T, YALE UNIV NEW HAVEN CT DEPT OF COMPUTER SCIENCE, *ALGORITHMS,...

The primary objective of this research is the development and demonstration of a global Failure Detection and Identification (FDI) Design Assistant (DA) prototype based on expert system technology. A global FDI algorithm performs its detection, isolation and estimation function by assessing the global effects of a hardware fault and surface damage on the closed-loop aircraft dynamics. Since changes in the flight control law affect the signature of a hardware fault and surface damage, the design...

Topics: DTIC Archive, Allen, S M, CHARLES RIVER ANALYTICS INC CAMBRIDGE MA, *EXPERT SYSTEMS, *FLIGHT...

We have obtained a number of results pertaining to image compression, robust estimation, and robust signal detection. All of this work has admitted the presence of data whose statistics are imperfectly known. Our results have featured adaptivity, flexibility, and nontraditional approaches. In order to employ more realistic statistical models, we have directed our research to admit nonstationarity and dependency. Much of our work in robust estimation and detection has employed a geometric...

Topics: DTIC Archive, Halverson, Don R, TEXAS A AND M UNIV COLLEGE STATION DEPT OF ELECTRICAL ENGINEERING,...

The development and performance of moving-bank multiple model adaptive estimation (MMAE) and control (MMAC) algorithms for quelling vibrations induced in the SPICE 2 space structure are analyzed in this thesis. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. The model supplied by Phillips Laboratory, Kirtland AFB is used to develop a truth model and multiple reduced ordered filter models. The filter models are developed from modal...

Topics: DTIC Archive, Gustafson, John A, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF...

Work in density estimation resampling has been carried out with Dr. Malcolm Taylor of BRL. Simulation based estimation has been applied to problems ranging from marketing to oncology. Two doctoral dissertations were written on the subject of nonparametric regression. The effects of more active public health intervention to halt the AIDS epidemic were considered. New algorithms for density estimation in several dimensions were developed. The estimation of the parameters characterizing a time...

Topics: DTIC Archive, Thompson, James R, RICE UNIV HOUSTON TX DEPT OF STATISTICS, *ALGORITHMS, DENSITY,...

The need for direct turbulence measurements in the upper ocean arise from widespread requirements to correctly parameterize momentum and scalar fluxes across the air/ocean interface. Until recently these observations were limited by a lack of instrumentation capable of measuring the fine-structure velocity field down to dissipation scales. The recently developed CDV package allows simultaneous sub-centimeter resolution measurements of temperature, conductivity, pressure, shear and the 3...

Topics: DTIC Archive, Coelho, Emanuel F, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *STRESSES, ALGORITHMS,...

This report presents a novel Kalman filtering approach to the suppression of narrowband interference from direct sequence spread spectrum communications systems. The algorithm is based on the digital phase-locked loop Kalman filter. Because the interference is assumed to be much stronger than either the signal or noise, the Kalman filter locks onto a function related to the interference. The net result is an estimate of the phase of the interference and its amplitude. The algorithm is...

Topics: DTIC Archive, Kozminchuk, Brian, DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO), *KALMAN...

This work covers one of the basic computational issues in materials science, which is that of devising algorithms for computing microstructure. Finite element discretizations are used to approximate a standard energy density functional. Grid effects are found to affect the solutions in some cases and suitable remedies are investigated. Covolume methods are a second topic of research. Three dimensional error estimates are obtained. A new and optimal Voronoi-Delaunay mesh generator is given....

Topics: DTIC Archive, Nicolaides, Roy A, CARNEGIE-MELLON UNIV PITTSBURGH PA, *MICROSTRUCTURE,...

We studied the pollution-error in the h-version of the finite element method and its effect on the quality of the local error indicators (resp. the quality of the derivatives recovered by local postprocessing) in the interior of the mesh. Here we show that it is possible to construct a-posteriori estimates of the pollution-error in a patch of elements by employing the local error indicators over the entire mesh. We also give an adaptive algorithm for the local control of the pollution-error in...

Topics: DTIC Archive, Babuska, I, MARYLAND UNIV COLLEGE PARK INST FOR PHYSICAL SCIENCE AND TECHNOLOGY,...

This report discusses the implementation of one of the best digital cyclic spectrum (CS) algorithms derived so far, the Strip Spectral Correlation Algorithm (SSCA). Some theoretical background and a detailed description of the SSCA are provided. An analysis of the SSCA is performed and an algorithm for mapping the SSCA output is formulated. The cyclic feature function (CFF) is defined as a means to detect the cyclic features from the SSCA. Results of the SSCA encoded in C are then reported....

Topics: DTIC Archive, April, Eric, DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO), *ALGORITHMS,...

Delaunay-Voronoi mesh systems provide a generalization of the classical rectangular staggered meshes to unstructured meshes. In this work it is shown how such covolume discretizations may be applied to div-curl systems in three dimensions. Error estimates are proved and confirmed by a numerical illustration. (AN)

Topics: DTIC Archive, Nicolaides, R. A., INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING...

This optical oceanography project provided support to researchers doing ocean optics experiments by developing analytical methods for solving multiple-scattering inverse and forward problems of radiative transfer, including: (1) Solutions of inverse problems that can be used to determine the spatial dependence of internal sources and/or inherent optical properties (IOPs). The sources of interest can arise from inelastic scattering effects, bioluminescence, or fluorescence, while the IOPs of...

Topics: DTIC Archive, McCormick, N. J., WASHINGTON UNIV SEATTLE DEPT OF MECHANICAL ENGINEERING,...

This report describes a new wave-prediction model called CGWAVE. CGWAVE is a genetal-purpose, state-of-the-art wave prediction model. It is applicable to estimation of wave fields in harbors, open coastal regions, coastal inlets, around islands, and around fixed or floating structures. Both monochromatic and spectral waves can be simulated with the CGWAVE model. While CGWAVE simulates the combined effects of wave refraction-diffraction included in the basic mild-slope equation, it also includes...

Topics: DTIC Archive, Demirbilek, Zeki, ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS, *USER...

The full scope of this research is to develop a robust and reliable circadian phase estimation system, and use it for model identification and light-based control design. The objective of this project is to develop preliminary results in the following directions to lay the foundation of the full research. 1. Circadian phase estimation and control: Demonstrate the applicability of the adaptive notch filter (ANF) to extract circadian phase from noisy Drosophila locomotive activity measurements...

Topics: DTIC Archive, Wen,John T, Rensselaer Polytechnic Institute Troy United States, circadian rhythms,...

The purpose of this report is to introduce an adaptive estimation and parameter identification scheme which the authors call Multiple Model Estimation Algorithm (MMEA). The MMEA consists of a bank of Kalman filters with each matched to a possible parameter vector. The state estimates generated by these Kalman filters are then combined using a weighted sum with the a posteriori hypothesis probabilities as weighting factors. If one of the selected parameter vectors coincides with the true...

Topics: DTIC Archive, Athans, Michael, Chang, Chaw-Bing, MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB,...

Efficient algorithms have been developed recently which utilize the specialized structure of the linear programming formulation for the problem of least absolute value estimation. These algorithms generally proceed in the direction of steepest descent along an edge of a convex polyhedral surface. However, we will show that the extreme point path of steepest descent may not be taken when degeneracy occurs. We will also present a criterion that determines the basic edge for steepest descent....

Topics: DTIC Archive, Armstrong,R D, TEXAS UNIV AT AUSTIN CENTER FOR CYBERNETIC STUDIES, *ALGORITHMS,...

The overall objectives of the subproject are to develop career paths that enable junior officers to make long-term career plans and to assist the Navy in developing assignment strategies that increase career retention of quality Naval officers. The study was undertaken to identify patterns in the duty assignment system that are associated with retention. If patterns are identified that are controllable through the assignment system alternative strategies that increase retention may be...

Topics: DTIC Archive, Weitzman, R. A., NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *CAREERS,...

This paper presents a recursive algorithmic implementation of the prewindowed high performance method of ARMA spectral modeling as described in Part 1. This algorithm provides updates of the ARMA models optimal autoregressive coefficients (in actuality prediction errors) as each new data point becomes available. The algorithm is computationally fast in the sense that it requires O(p) multiplications and additions for each update. It is shown that this fast recursive algorithm may be implemented...

Topics: DTIC Archive, Cadzow,James A, VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF...

This paper presents a recursive algorithmic implementation of the prewindowed high performance method of ARMA spectral modeling as described in Part 1. This algorithm provides updates of the ARMA models optimal autoregressive coefficients (in actuality prediction errors) as each new data point becomes available. The algorithm is computationally fast in the sense that it requires O(p) multiplications and additions for each update. It is shown that this fast recursive algorithm may be implemented...

Topics: DTIC Archive, Cadzow,James A, VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF...

The development of a model to estimate 30 and 50 kt wind probabilities from tropical cyclone forecasts is described. Some examples to illustrate the use of probabilities are discussed. The model is based on position forecast errors, which are used to determine the probability of a cyclone occupying a particular geographical position, and on wind profile errors. Wind profile errors consist of errors in the forecast maximum wind and errors in the forecast radius of 30 and 50 kt winds. The profile...

Topics: DTIC Archive, Jarrell,Jerry D, SCIENCE APPLICATIONS INC MONTEREY CA, *WEATHER FORECASTING, *WIND...

An algorithm has been developed which estimates the range bias error from measurements made by radars on two platforms within a common detection area. The radars on the platforms each measure the position of two common targets and the difference vector between the measurements. Using a number of these measurements, a least square estimate of the range bias error is determined. (Author)

Topics: DTIC Archive, Prather,D D, NAVAL RESEARCH LAB WASHINGTON DC, *RADAR TRACKING, *RANGE FINDING,...

This report describes the implementation and experimental evaluation of a proposed decision aid to support naval Task Force Commanders. The decision aid, named the Sketch Model, enables a human operator to specify his subjective estimate of a multidimensional, multimodal, unsymmetric three dimensional function by electronically sketching its two-dimensional projection (e.g., iso-altitude contours of a three dimensional function) on a computer graphics terminal. The Sketch Model is hypothesized...

Topics: DTIC Archive, Irving,Gary W, INTEGRATED SCIENCES CORP SANTA MONICA CALIF, *DECISION MAKING,...

A simple differential equation for the triangular square-root of the error covariance of the linear state estimator is derived. Previous algorithms involved an antisymmetric matrix in the square-root differential equation. In the constant model case, Chandrasekhar-type equations are shown to constitute a set of fast square-root algorithms for the derivative of the error variance. Square-Root algorithms for the smoothing problem are presented and as in the discrete case, an array method for...

Topics: DTIC Archive, Morf,M, STANFORD UNIV CALIF DEPT OF ELECTRICAL ENGINEERING, *STOCHASTIC PROCESSES,...

The maximum entropy spectral analysis (MESA) technique is applied to a linear spatial array of sensors to obtain wavenumber power spectra. The resultant wavenumber spectra are compared with conventional beamsteered antenna patterns using simulated signals mixed with Gaussian noise. The results indicate that the MESA technique, which is an all-pole model, may provide improved accuracy and improved spatial resolution of signals under varying signal-to-noise conditions. Some difficulties with MESA...

Topics: DTIC Archive, King,William R, NAVAL RESEARCH LAB WASHINGTON DC, *POWER SPECTRA, *ANTENNA RADIATION...

The Maximum Likelihood estimators for the Neyman Type A distribution parameters are very difficult to compute. In this thesis, the Empirical Probability Generating Function is used to provide estimators that are easier to compute and have asymptotic efficiency at least as high as 97% of that for the Maximum Likelihood estimators over most of the parameter space considered. The estimators found by this method are consistently better than the Method of Moments and the Method of Zero Frequency...

Topics: DTIC Archive, Bishop,Harold R, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *PROBABILITY DISTRIBUTION...

The process of tracking and localization of a moving acoustic source in the ocean has a natural formulation as a problem in nonlinear filtering theory. In general, the optimal estimator for this signal processing problem cannot be explicitly constructed nor can optimal performance be computed. However, optimal performance can be approximated by using mathematical algorithms which provide lower bounds on attainable estimation accuracy. Lower bounds on tracking and localization errors are...

Topics: DTIC Archive, Galdos,Jorge I, ANALYTIC SCIENCES CORP READING MA, *UNDERWATER ACOUSTICS, *ACOUSTIC...

The quadtree representation encodes a 2(n) by 2(n) binary images as a set of maximal blocks of 1's or 0's whose sizes and positions are powers of 2. With the aid of the quadtree, a hierarchy of approximations to the image can be defined. Several ways of doing this are described. The accuracy of these approximations is empirically evaluated by studying how fast estimates of the first few moments of the image, computed from the approximations, converge to the true values. Approaches to the...

Topics: DTIC Archive, Ranade, Sanjay, MARYLAND UNIV COLLEGE PARK COMPUTER VISION LAB, *ALGORITHMS,...

In this paper we develop a comprehensive framework for the study of decentralized estimation problems. This approach imbeds a decentralized estimation problem into an equivalent scattering problem, and makes use of the superposition principle to relate local and centralized estimates. Some decentralized filtering and smoothing algorithms are obtained for a simple estimation structure consisting of a central processor and of two local processors. The case when the local processors exchange some...

Topics: DTIC Archive, Levy,Bernard C, MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INFORMATION AND DECISION...

The theory of large deviations is applied to the study of the asymptotic properties of the stochastic approximation algorithms. The method provides a useful alternative to the currently used technique of obtaining rate of convergence results.

Topics: DTIC Archive, Kushner,Harold J, BROWN UNIV PROVIDENCE RI LEFSCHETZ CENTER FOR DYNAMICAL SYSTEMS,...

This work investigated the detection of pulses and extraction of modulation parameters from different types of time-limited chirp signals, as may be found in pulse- compression radar signals. The work is split into two parts. The first part examines the pulse detection problem, i.e., the detection of the pulse start/stop times. Such information can be used to determine the pulse width and repetition rate of the radar systems under investigation in an automated fashion. We compare the robustness...

Topics: DTIC Archive, Hippenstiel, R, NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF ELECTRICAL AND COMPUTER...

The H-function is the most general special function, encompassing as specific cases many mathematical functions and nearly every continuous statistical distribution defined over positive x. A general procedure is developed to estimate the parameters of the H-function which gives the best fit to a set of data. The technique creates a system of nonlinear equations from the method of moments and uses Powell's quasi-Newton hybrid algorithm to solve the equations. A computer program, which can...

Topics: DTIC Archive, Bodenschatz,C D, AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF...

Symposium topics include: An Integrated Gear System Dynamics Analysis over a Broad Frequency Range; Coupled Torsional-flexural Vibration of a Geared Shaft System Using Finite Element Analysis; Influence of an Axial Torque on the Dynamic Behavior of Rotors in Bending; Sensitivity Analysis of the Locations of the Balancing Planes of an Unbalanced Rotor-Bearing System using Dynamic Condensation Technique; Structural Damage Detection by the System Identification Technique; Time Domain Modal...

Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC SHOCK AND VIBRATION INFORMATION CENTER, *MACHINES,...

An algorithm is presented for the consistent recovery of replicated data in a client-server system. The algorithm is based on logging and is similar to the optimistic techniques that are well known in the literature. However, unlike in existing optimistic techniques, explicit dependency information is not maintained. Instead, dependency information is estimated from the ordering of messages found in servers' logs. These dependency estimates can, in general, be expensive to compute. It is...

Topics: DTIC Archive, Kane, Kenneth P, CORNELL UNIV ITHACA NY DEPT OF COMPUTER SCIENCE, *QUEUEING THEORY,...

An algorithm which can accurately reconstruct an aircraft target trajectory from pre-recorded digital radar plots is described. Periodically recorded track data from a tracking system provide the coarse target position and speed estimates required by the algorithm. The algorithm has been applied in the operational analysis of the RAAF AN/TPS-43F(V)-1 surveillance radar and Myriad tracking systems at the No.2 Control and Reporting Unit (2CRU), Darwin, using data acquired during exercise Pitch...

Topics: DTIC Archive, Scholz, M L, WEAPONS SYSTEMS RESEARCH LAB ADELAIDE (AUSTRALIA), *PLOTTING, *AERIAL...

A numerical and experimental study of time domain methods for modeling and parameter identification of structural systems is presented. Models are developed which can be used to predict the transient response of multiple- degree-of-freedom systems subjected to arbitrary input. The linear, discrete time transfer function is expressed in a form called the Autoregressive Moving Average (ARMA) model. The ARMA model is a minimum parameter model that may be parameterized with a minimum number of...

Topics: DTIC Archive, Batill, Stephen M, NOTRE DAME UNIV IN DEPT OF AEROSPACE AND MECHANICAL ENGINEERING,...

Quantitative information of individual component contribution from multiexponential data is obtained by a reiterative, linear least-squares algorithm. Uncertainty in the parameter estimates, arising from uncertainty in the data and overlap in the response, are predicted from first principles. The analysis method includes weighting to account for the Poisson error distribution arising from shot-noise limited signals, which increases the accuracy of the amplitude estimates. While the algorithm is...

Topics: DTIC Archive, Wong, A L, UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY, *FLUORESCENCE, *ESTIMATES,...

An Autonomous Underwater Vehicle (AUV) is an unmanned submersible vehicle capable of performing a variety of missions. The AUV, which is the subject of this research, is a small prototype vehicle equipped with various control surfaces as well as telemetry devices which provide pertinent measurements of the vehicle states. This research is directed toward the development and implementation of a digital-control program which provides robust depth control of the vehicle. An adaptive parameter...

Topics: DTIC Archive, Williams, James M, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *UNDERWATER VEHICLES,...

In this paper we present a new class of language models. This class derives from link grammar a context-free formalism for the description of natural language. We describe an algorithm for determining maximum-likelihood estimates of the parameters of these models. The language models which we present differ from previous models based on stochastic context-free grammars in that they are highly lexical. In particular they include the familiar n-gram models as a natural subclass The motivation for...

Topics: DTIC Archive, Lafferty, John, CARNEGIE-MELLON UNIV PITTSBURGH PA SCHOOL OF COMPUTER SCIENCE,...

The fast multipole method (fmm) for calculating electric fields developed by Greengard and Rokhlin (J. Comp. Phys. 73, 325(1987)), has been implemented specifically for molecular dynamics simulations of electrochemical problems including boundary conditions associated with metal electrodes. This order N (number of charged particles) algorithm, is known to be computationally much more efficient than direct or Ewald sum methods (order N 2) for systems with as few as one thousand charged particles...

Topics: DTIC Archive, Glosli, James N, IBM ALMADEN RESEARCH CENTER SAN JOSE CA, *SIMULATION, *ELECTRIC...

We discuss mesh-moving, static mesh-regeneration, and local mesh- refinement algorithms that can be used with a finite difference or finite element scheme to solve initial-boundary value problems for vector systems of time-dependent partial differential equations in two space dimensions and time. A coarse based mesh of quadrilateral cells is moved by an algebraic mesh- movement function so as to follow and isolate spatially distinct phenomena. The local mesh-refinement method recursively...

Topics: DTIC Archive, Arney, David C, RENSSELAER POLYTECHNIC INST TROY NY, *ALGORITHMS, *TIME DEPENDENCE,...

Passive acoustic ranging (PAR), based on acoustic Doppler shifts, has been proposed as a suitable method for extracting velocity and range information from a source which emits a time-dependent acoustic signal. Operational constraints on the PAR method were evaluated and estimates were made of the limitations of realistic operation under various environmental conditions. In addition, performance of the PAR method was evaluated for multiple helicopters. Several methods of analysis of signals...

Topics: DTIC Archive, Carnes, Benny L., ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS STRUCTURES...